Studies will continue on the physiologic role of 16-hydroxylated steroids in health and disease. Of immediate clinical concern is the monitoring of fetal distress employing radioimmunoassay techniques to assess maternal plasma levels of 16 alpha-hydroxyprogesterone and unconjugated estriol. Studies in human volunteers will focus on the inter-relationship of 16 alpha-hydroxyprogesterone to the regulatory hormones in the female menstrual cycle. The rhesus monkey will be utilized in studies of ovarian physiology, evaluating the effects of 16 alpha-hydroxyprogesterone on follicular development and lutenization including steroid production.